variable '__Levelfoo_app13' unsafe in 'case'

[rlipscombe]

To reproduce, put two lager statements on the same line.

src/foo_app.erl:13:26: variable '__Levelfoo_app13' unsafe in 'case' (line 13, column 5)
src/foo_app.erl:13:26: variable '__Pidfooapp13' unsafe in 'case' (line 13, column 5)
src/foo_app.erl:13:26: variable '__Tracesfoo_app13' unsafe in 'case' (line 13, column 5)

The exact variable name is generated from the module name, so you'll get a slightly different compilation error. The cause is presumably that the line number is in the generated name as well, and there's a collision.